This feature would be nice.  It isn't trivial to implement, though.  I can see about adding it in 3.16.

In the Project options> File locations> Mods and Libs tabs:
It would be a help if existing entries were editable.

At the moment, if we want to amend a long pathname that has already been set for one of the file location entries, the only way this can be done is by entering the amended pathname as a new file location, and then selecting and removing the old one that the new one replaces.  This is how it is with the MacOS version of SF, and I assume the other versions are similar but I haven't checked.

I suggest that a great improvement in this small detail would be obtained if existing entries could be made editable, either in-situ, or by having them appear in the already-editable browse/add field whenever selected.
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John