Why does memory keep rising in the editor?

This apparently was a bug fixed in 4.11? But I am on 4.25!
I start at around 3.7Gb when I launch. Then 4.8Gb when I open my scene.
And it gradually keeps rising without me adding more assets.

And I also get an ‘Out of video memory error’ when I try and save the current scene under a new name, followed by a crash.

So I am a relative novice and have a lot to learn but don’t see why this is happening?

Can someone tell me, does the total memory footprint of your textures play a part?
I have several 8k textures.
And what about mipmaps. Does enabling mipmaps on your textures have any impact on the memory footprint?

Thanks in advance for any replies!