While not very user friendly, this will work, if you have any custom css addon for your browser. If it is assets, you need to change the scope accordingly. Or just remove "games", but this might affect your library.
And addon to add things to the list with a mouse click would be nice, but this is beyond my abilities. Copy link/accountname/gamename to the url in question and paste above a placeholder, duplicate lines for next time insertion. Rinse, repeat. The underscores are for easy doubleclick selection. Tested with Stylus 1.5.41.
(the !important deals with page loads in endless scroll)
@-moz-document url-prefix("https://itch.io/games") {
div.game_cell:has(a[href*="paste_full_link_to_game_inside_quotes"]) { display: none !important}
div.game_cell:has(a[href*="paste_full_link_to_game_inside_quotes"]) { display: none !important}
div.game_cell:has(a[href*="paste_full_link_to_game_inside_quotes"]) { display: none !important}
div.game_cell:has(a[href*="//or_ignore_a_publisher.itch"]) { display: none !important}
div.game_cell:has(a[href*="//or_ignore_a_publisher.itch"]) { display: none !important}
div.game_cell:has(a[href*="//or_ignore_a_publisher.itch"]) { display: none !important}
div.game_cell:has(a[href*="itch.io/or_ignore_games_starting_with"]) { display: none !important}
div.game_cell:has(a[href*="itch.io/or_ignore_games_starting_with"]) { display: none !important}
div.game_cell:has(a[href*="itch.io/or_ignore_games_starting_with"]) { display: none !important}
}