Swell, little swell, or closed accent indication for Lines Palette

In the Lines Palette, please add a single item that would be a pair of hairpins (cresc-dim) that can be anchored on one note or on several notes, especially ones that are tied together. This indication is very commonly used, especially in 19th century classical music. Normally, for this specific usage the cresc & dim hairpins are symetrical and also vertically aligned, but the overall width and horizontal placement should be adjustable. This is an old, brief discussion: https://musescore.org/en/node/126021
In that discussion was this link, with descriptions that I thought were helpful.
https://www.dolmetsch.com/musicalsymbols.htm "swell, closed hairpins (over a phrase) or closed accent (over a single note): to increase volume and then die away in the duration of a single note or short phrase also called messa di voce (Italian) or mise de voix (French)." or "in nineteenth-century German non-vocal music the < > sign can represent a stress or accent as opposed to a crescendo followed by a decrescendo music. In such a case, the marking apparently indicates a kind of "warm", not too powerful, accent with implication of vibrato where appropriate [suggested by Ron Evans]"

For playback purposes, implementation could be subject to much debate and possibly complicated. If anything like a modest, rounded swell isn't possible, I would suggest something like a 10% increase in volume for the duration of the note as a short term solution. This is the kind of indication that is so open to performer interpreation that making everyone happy about the playback solution isn't like to be possible. Sorry 'bout that in advance... ;-)
Thanks.