Short answer: For the general case, no.
Your question asks about both the general case, and an outlier case of suicide. That series of articles in the Catechism addresses in part whether or not the disordered act of suicide is with full consent of the will, or not. If it isn't it may not meet the gravity of mortal sin during judgment. That's in the hands of our Lord.
General case: the point of repentance is to turn toward God during this life.
CCC 1021 Death puts an end to human life as the time open to either
accepting or rejecting the divine grace manifested in Christ.
The hope for salutary repentance is an edge case, as this repentance something that can only be given by God. How this may happen is neither known nor taught by the Church. It's in God's hands.
- All repentance (especially for a grave sin) comes from God. We are
incapable of contrition without grace (from @AthanasiusofAlex comment)
CCC 2283 We should not despair of the eternal salvation of persons who have taken their own lives. By ways known to him alone, God can provide the opportunity for salutary repentance. The Church prays for persons who have taken their own lives.
If there is a hope for salutary (beneficial) repentance, it would logically happen at particular judgment. We (the faithful) don't know. We can only hope and pray. (It never hurts to ask).
CCC 1037 God predestines no one to go to hell; for this, a willful
turning away from God (a mortal sin) is necessary, and persistence in
it until the end. In the Eucharistic liturgy and in the daily
prayers of her faithful, the Church implores the mercy of God, who
does not want "any to perish, but all to come to repentance":
At judgment, will Jesus find that this soul has willfully turned away from God, to the last, or not? The truth cannot be hidden at judgment.
CCC 1033 To die in mortal sin without repenting and accepting God's merciful love means remaining separated from him for ever by our own free choice.
Did the suicide willfully separate themselves from God by their own free choice? Jesus will see the truth of the matter, and judge accordingly.
Once the person is dead, all that the Church can do is pray for them. This includes the Church Triumphant (most importantly Mary, Mother of God) to whom prayers of intercession are offered with great frequency.
Holy Mary, Mother of God, pray for us sinners, now and at the hour of our death.
This intercessory prayer asks Mary to make an appeal for a sinner to her Son, an appeal to mercy. Jesus sits on the throne of judgment. Mercy is within his authority.
Kyrie eleison (Lord have mercy), Christe eleison (Christ have mercy)
The basic question
I'm curious about the phrase "salutary repentance." Does this mean that someone in Hell can repent?
From the above, salutary repentance (if given) would happen at judgment. Once particular judgment is complete, alea iacta est. Since one does not go to Hell until after particular judgment, it would then follow that once in Hell the chance for repentance (of any sort) is moot.
To be clear, an assumption that the soul (suicide) in question is in Hell before a chance at that possible salutary repentance is unsupported by current Catholic teaching. Judgment comes first, and then one is either with God, no not.
1030 All who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven.
The question whose answer is known only to God and the person now dead is whether or not the person was in friendship with God (perhaps imperfectly purified) or if that person had, in their heart, willfully turned their back on God and remained unrepentant to the end.
I. The Particular Judgment
CCC 1022 Each man receives his eternal retribution in his immortal soul at
the very moment of his death, in a particular judgment that refers his
life to Christ: either entrance into the blessedness of heaven-through
a purification or immediately, or immediate and everlasting damnation.
The willful act of turning away from God and obstinately refusing to turn back toward Him is the surest way to damnation.
In a particular case, is it possible to be offered the chance to turn back toward God when facing particular judgment? With God, all things are possible (Matthew 19:26)
Jesus will know the truth of what is in one's heart. Whether or not salutary repentance is given is wholly in the hands of God. All we can do is pray for God's mercy. So we do. We Catholics offer prayers for the dead.