Maybe I’m the only one who didn’t know this, but Aves supports built-in video editing, which was a feature I loved from the non-libre version of Simple Gallery, but well, we all know what happens with those apps.
I’m not using the Libre version of the app so this feature may be not available in that version, but both the Libre and this one are available in the F-Droid (or IzzyOnDroid) repositories, as far as I understand the only difference is some proprietary libraries, but I’m not sure at all about this, so please correct me if I’m wrong.
The Fossify Gallery app, which is basically just a fork of Simple before it got screwed up, has (I think) the same video editor that Simple had. So, if you liked that one, you could always try Fossify. Unless Aves is better of course :-)