When you set shortcuts on the controls (checkbox, button) with & in the cText property, the letter does not appear underlined. This happens only when we open the form with the mouse, in the main menu. If you open the form by using the keyboard, all letters (with &) are underlined correctly: [ ]&Filter) / [ ]Filter.
This happens in Xailer 4.x and 5.x, but with a difference. In 5.x, when you open the form with the mouse (it does not display any underlined letter), when you type and release the ALT (left), the letters are underlined.