Hi,
I have been using DesignSpark since V3 and now on V5 like you.
If the ModelSource button disappears, then it's prrobably undocked or floating, but thats not a problem as you can open it with CTRL+M shortcut or from View on the Menubar where it is at the bottom of the list.
I'm sure you solved this and found the tutorials at **broken link removed** , but thought I would post as a fellow DSPCB user.
There are now over 20 tutorials with user knowledge items as well.
I have been sold on DesignSpark PCB since version 3 where it was the best free software I found for my board size requirements which forced be to abandon the free Eagle due to it's limitations.
I'm now starting a 4 layer board in DSPCB which is a new venture for me, but essential for my mixed signal requirements.
How are you doing with DSPCB? I'll have a look round for a group to join. I only started on this forum for 'electronics' help, but now excited at the expertise here.