The Katana 'Boost' effect has a 'Solo' control which consists of a level and an on/off switch. When solo is switched on, you get a mild increase in boost effect which can 'lift' your guitar sound when you are soloing. The level control determines how much of a 'lift' is applied. The on/off switch turns this feature on and off.
You can map the 'Solo' function to a character / key code on your bluetooth footswitch to enable this feature to be turn on/off whilst you are playing.