^^^ That doesn't seem to help me, Brian. The suggested themes still stay there and no option to remove them appears.
I've not got a problem with those suggested topics of interest, ImLostAgain, but I can see that they might possibly be awkward for someone whose computer screen can be viewed by others. To the best of my knowledge, there's no way of getting rid of them while one is logged into YouTube under a particular channel name but, I didn't want to see them, I could just switch to one of my other three channel names.
For example, I'm currently logged into YouTube under my most frequently-used channel name and I'm seeing 'Tourist attractions', 'Trains', 'Air traffic control', 'Aircrafts' (sic), 'Radios', 'Ships', etc. If I wanted to remove them (or, at least, replace them with something else), I could simply click on the icon for my channel at the top right of my screen and select 'Switch accounts'. I'd still be logged in under my sole YouTube email address and password but I'd then be using a different channel, thus losing the topic suggestions that I'm currently seeing.
I find it quite handy to have several different YouTube channels, even if some of them don't have any videos uploaded to them. Then I can choose to post a comment either under my own name (which is used for my main YouTube channel) or under an alias (used for an alternative channel).