@darkmiss - welcome to MobileRead.
Definitely not a stupid question and yes you can certainly do that. Whether you have one or multiple columns is up to you - it is possible to do it in a single column if you want to. Think of the "tags" column in calibre - if you gave each list its own unique tag value, then you can see the combined result in the tags column.
Using a custom column is fundamentally no different - you could create a column which allows storing multiple values like tags does, or you could create a single yes/no column per list, or you could create a single text value column per list. It is entirely up to you.
As to the mechanics of creating a custom column, you might find
this blog post useful if you are new to them - they are a wonderful feature of calibre. Once you have your column setup, it is just a case of going into the Reading List plugin configuration and for each list setting the column name you want to update, the value you want to put into it.