Is there also a way to cut or extend the cable to whatever length you want?

Some parts are flexible(for example in "Rubbers and strings" category) and to modify them press F to bring up the nodes. There is no limit the stretch these parts but you'll have information about its current length and original length in the control window.

When it comes to tank threads you'll have to put them together by hand, since it's made of many same parts you have to manually snap and rotate each item to fit the gears/wheels they run around, unfortunatly. I bet there is already a suggestion to Scrubs to make a function for this aswell as all other thing on the ToDo list for Mecabricks development...

Edit: To find all flexible parts, go to the parts section and click on the gear wheel icon to see configurations. Uncheck Solid and Assembly and click "New configurations" and you'll see all parts that are flexible.

Okay thank you!