Tank boredom is a way of life for me.
I like
plecos. Plecos like to hide. I like happy plecos so there are plenty of places to hide. This means often a tank can look empty. I have added movement fish to the tanks so they look less empty.
Dats also like to hide. So does Mr Biteytubefish.
Then there are tanks that are empty and waiting for a cool new find at the LFS or a breeding pair/group of fish to go into them. No real excitement in an empty tank.
Then there are dwindling tanks. By this I mean tanks that I'm tired of and waiting for its residents to get old and die. If this happens with a group of fish I can just give them away. In the case of my haplo tank it is now dow to 2 male hoplos due to murder fish getting murdery. The remaining female decided to become a boy, this is something I didn't know hoplos could do until her pectorals were red and most of the way to male sized. With murder fish in the tank this was a fatal decision on her part. So we have 1 female
hoplo in another tank. If she dies I'm out of the hoplo breeding game.
Murder fish looks like this. Hoplos, so cute until they decide it is mating time. Murder Fish defied all the advice I give to others. My surface was clear of everything and high flow constantly agitating the surface. The fish still decided it was mating time even though it can't build a nest. So it is now alone in a breeder.
That main tank also contains the eternal lambchop. 1 lambchop that I thought was 10 years old as we got it right after we move into the house. My wife says we moved in over 15 years ago.. You really can't give away a fish that is around 5x the species max age. I'm also not buying more, so I have a single immortal unhappy lambchop. As I was typing this I decided to again futilely try to get a picture of it. It looked like ironically, it might have died while I was typing about its immortality.. Nope, there it is!
Then there are tanks I'd like to swap fish out of. My emps are unfortunately ~18mo old now so I can't really sell them, I'd like to move in a different
tetra to breed (I missed out on some cool ones a while back). In another tank I'm getting bored with the rainbows and
congo tetras as movement fish. Man are those congos getting big.

Spot any plecos in that one? See it needs movement fish.
As for moving plants I move small ones or ones that have been dug up. I do not like moving monster swords that have huge root balls on them.
I also do not run any capped tanks. I imagine moving a plant in a capped tank is just a nightmare as when you pull it up it fills the tank with soil.
As a side note: I generally get bored with things quickly, so keep that in mind.