Problem: Reuse of high quality edit summaries is difficult because there is no way to select them again at a later date or to use them across devices. In some cases, the browser shows recent edit summaries but older edit summaries tend to disappear after a while so they have to be written again.
Proposed solution: If there was a way to configure, say, a few dozen edit summaries that one commonly uses, it's possible to reuse them whenever a similar edit is made in the future. The edit summaries would belong to the user's account so this allows the software to show them on other devices and improve the quality of edit summaries when making edits on mobile. In user preferences, a text field could be provided and each line could be interpreted as an edit summary. It'd be a place to define these user edit summaries and these are then made available in the editor when filling the edit summary. This could be done next to the dropdowns which are availabe when ticking the "Add two new dropdown boxes below the edit summary box with some useful default summaries" box under Preferences > Editing.
Who would benefit: Anyone who wants to provide a detailed edit summary. The benefit of this feature is that you'd only need to write a long detailed edit summary once (possibly with links to relevant policies) and it'd be easy to reuse.
More comments: In en.wiki, there is now an option to tick "Add two new dropdown boxes below the edit summary box with some useful default summaries" box under Preferences > Editing, which is helpful for common use. This particular proposal is to extend that functionality with user-specific edit summaries. Examples of edit summaries include: "new stub, passes <some policy>, point 3" or "changed formatting of number, see <some policy>". This proposal has been adapted from Community Wishlist Survey 2022/Editing/Custom edit summaries per user