Reported by @Jules78120 on my talk page on meta (permalink), with my reply for completeness:

1. [idea] Editing a filter is a chore because for long lines of regex, we have to scroll a lot. Idea: implementing automatic line wrap, as there is on coding softwares.
2. [idea] For the same reason, idea: the edit window should be ''larger'' (it is ridiculously small on my 21.5 inchees screen) and ''resizable''.
3. [bug] There are two edit software in Abusefilter. With the first one, sometimes (apparently because of some special letters) the mouse cursor is not shown where it is really. This is super-annoying, obviously.

1. I think implementing line wrap might be doable. As a workaround, what I usually do is to break down regexps using string concatenation ("+"), which, I recognize, has some drawbacks.
2. This is a good point, in particular making it resizable. However, I'm not sure if Ace editor (the one with syntax highlighting) is resizable, I'd have to check the docs.
3. Yep, this is a known bug. And actually, this is also a bug in Ace editor, see for instance [https://github.com/ajaxorg/ace/issues/3037 here] and [https://github.com/ajaxorg/ace/issues/4434 here]. OTOH, I just tried to reproduce the bug but I haven't been able. I'm sure it used to happen more frequently in the past, and for more special characters. Unfortunately, there's not much we can do about that :-/