Modern Events Categories

I have a page where I want to add events that users can see and join. In my company, these events have two categories and I want users to filter only by these two categories (by Category, I mean the option available when adding  new event as you can see in this link). However, SharePoint provides a bunch of default categories (e.g. Gift, Anniversary, Work hours, etc.) that the user can select from and which I do not want (see below).

Is there any way to remove them and keep only my desired categories? Please note that I found a thread  that seems possibly to address the same problem (see here). However, the suggestions given require changing lists through Page Properties, an option which I don't seem to have in the first place (see below)!

Please help 🙏

Thanks

Beshr