Squid allows you to modify the number of steps in a looping pattern from 1-64 steps, with default being 16 steps aka 1 bar.
Therefore, the easiest way to have a 10/8 pattern on the Squid is to create pattern with 18 steps. Any of your 16 sequencer tracks (aka layers) that you want playing in 10/8 must have a pattern length of 20. To do this:
1) Start with a default pattern, the length is usually set to 1-bar.
2) Hold SHIFT and give a single tap the Left Arrow button (above your 16 step grid).
3) On screen you will see the 2 of the 4 rectangles have been illuminated. This means you now have a pattern length of 2 bars.
4) by using the Left and Right Arrow buttons, you can navigate back and forth between your two bars, allowing you to place triggers throughout your pattern.
5) after having navigated to the 2nd bar of your pattern, you can now modify the length of that second bar to only 2 steps
6) To do this, find the center column of function buttons right down the middle of the unit. The last button is called ACTIVE. Press it.
7) Now you're in the mode where you can DE-ACTIVATE steps from your pattern. So just tap STEP BUTTONS 5 through 16 and see how they turn off. You've just deactivated all but 4 steps from Bar 2 of your pattern. So you have an 20 step loop. Which is a form of 10/8
8) If you want this 20-step loop to go at half speed in relation to all your other tracks...just turn the COUNT KNOB (lower right hand corner) one click so that every step in your 20 step pattern lasts 2 counts instead of one...so therefore this pattern is going at half speed.