Then you are making a mistake, and you told me what you did... Hang on... You save the tree in the tileset in Paint and reload in Advance Map, and the tree is unchanged? Try reopening the file in Paint.
... They wouldn't appear in the map itself, as they aren't set to a Tile Space. You need to do that yourself (They should appear in the middle Box thing in Block Editor, at the bottom) (Tutorials are your friend)
First I open A-map then I open the block editor then I save tile set 1 with pal 0
I open it up in paint then I open the other tiles that have and want to import
I copy the tiles and replace them with the tiles I want to edit in tile set 1
I save it, then load it into the block editor
Search for one there. There are tons of ROM Bases, and also, you need patience. Try it again, this time make sure you record each step EXACTLY you take, and if it doesn't work, that then tells me exactly what you have done. Then I can follow it and see the mistake.