There are actually a huge number of directions in terms of developing plugins that you can expand your portfolio. Another question is whether the monetization of this plugin.
Give examples of some plugins:
1) Html Import 2 - https://wordpress.org/support/plugin/import-html-pages/
once there was a plugin that was designed to import posts and pages from the html pages. You can specify CSS selectors and the path to the file and it downloaded everything needed. Also doing redirects. Of course this can be done writing a simple parser, but for the end user who does not own programming languages, I think it will be difficult.
2) I would say that not enough normal Yandex Maps. Especially, for integration with third-party plugins. For example, ACF + Yandex Map. They sort of are, but the lame leg
In General, you can delve into the repository of VP and see old plugins that no longer work with new versions of VP. And then just to modify / update them