help with scaling manually

So i encounter this problem that i can not find solution because i don't now the correct words to search it.

https://imgur.com/a/W5zekiy

I have 3 cubes, with some space in between them, the one in the middle, i need to resize it, to fill the empty space between the others 2, to make for example, some bridge between them.
Is there an option to scale it, in a way similar as snapping for position? in other words, scalling until colition, or between verts or any other option its available to scale to perfect shape in between 2 objects

 

No, there's no editor help for that. But you can use math. For example, space the two side cubes 2 units apart, and then the scale of the center cube should be 2 (since cubes by default are 1 unit on each side).