How to use 'while pressed' options in layouts?

[VitaminCPP]

In layout options, under group 'keys to change layout', there are some 'while pressed' options, like Left ALT(while pressed). When I check this option, Left ALT doesn't work at all (ALT+Tab doesn't work, for example). When I press Left ALT or Hold it or whatever, the layout doesn't change.

How do I change layout with 'while pressed' key options? What am I supposed to do EXACTLY?

Thanks.