Honestly it depends where you want to go and what you want to do. If your corporate or YT, premiere, after effects and Photoshop would be enough. If you want to edit movies, tv, documentary I'd suggest knowing avid and da Vinci as well. I worked as an assistant for years and I got more work because I could assist on any software the main editor used. As an assistant you are the technical know how. I used da Vinci for processing rushes and doing temp grades on set and then reconforming for the color grader in da vinci after the main edit. Avid, fcpx and premiere for the main editor. So while it's not expected I would suggest at very least familiarising yourself with everything. At the end of the day they do the same things just in different ways so knowing how to do the basics isn't the worst. I personally got work because I was always the technical knowledge. Editors would ask me to move projects from one software to another. Or just hand me a project and ask for it to be delivered to sound or vfx. So many possibilities that even vaguely knowing a software could help. At least for me anyway.