Looking for an editor which does this?

All the popular editors do this – I use premiere and you select the insert mode and then at the cursor it inserts the new clip, shifting everything else rightwards, you can then you the other edit modes to trim it.

DaVinci Resolve also does this. Very similar to Premiere. There is a very capable free version.

I think the trouble is they hide the little buttons that make these things toggle, and if you don’t know how to engage a facility, you’re stuck. Premiere, for example, as a nice feature that actually lets you grab everything on the right of the cursor, so you can drag everything forward to create a ‘hole’for the new clip, or you can do it automatically. Oddly, I don’t tend to use the auto facility – and I don’t know why?

Edit functions are on the edit page right above the timeline in Resolve.

DaVinci Resolve is free