Easy-peasy answer: you’re looking in the wrong place. Put the cursor (not play head) on the left (earlier) side of the cut. A red line will show up. Right -click and there’s your Merge with next clip. Easy-peasy!
Why do it this way? The secret’s in the wording: Merge with next clip. If you’re to the right (later side), what if there’s no next cut? What if that cut’s out of the screen and maybe you want to merge it, maybe you don’t. Cursor to the left, little red line, right-click… hello, success!
(And, yes, I should stick with decaf)