It's really easy to add tables. I think you can do it in the Links Admin, if not, you can do it at the mysql prompt -- or if your server runs PHP you can install the phpMyAdmin program, and it becomes trivial.
Actually, Alex has the guts of the routines to allow you to define a table, then add it through the setup.cgi That might be a quick and dirty mod -- changing the setup.cgi to allow addition of tables as well as drop/create the whole database.
I don't use PHP on my server, but I have compiled it into Apache so _I_ can use a lot of features, and I might even make a PHP enabled bbs available. It does make coding for mySQL easier in some respects, but it's a server-side scripted language and as such, has more 'state' issues than Perl or Java. It is written to work closely to MySQL, so it does have that major advantage... and a lot of people are playing with it since it doesn't require cgi access or understanding Unix to work with it --- it's sort of like a Visual Basic in a Perl world.
As for the alternate categories.... I'm not clear on how they work. I have a feeling that when a more robust solution to the extensive category lists and having to enter category names as /name/name/name appears, it will cascade over to the alternate categories as well.
If you can't figure out how to add a new table, I'll write up some documentation, since for most of us it's second nature already
It's actually a lot esier than it seems, and it makes adding features really easy once you get the hang of it.
Each table can hold a collection of data, and you can relate it to other tables through common fields, which can then be 'joined'
In trying to attach things to the LinkID of Links Table, you need to add a field "LinkID" just like on the validation table, and store it. If you add an auto-inrement field as the first field of your table, you will always have a unique identifier. Most things in LinkSQL are related through the LinkID, which is the auto-increment field of the Links table.
The nice thing about SQL is that adding tables (files) means literally that -- just adding them. You don't have to deal with any of the code to manage them -- that's all part of the SQL engine, and all the higher-level featurew of LinkSQL are available too.