Visio 2013 - Format Shape Task Pane: Using hotkeys?

[visiofox]

Hello again,

how can I use the hotkeys - I mean the underlined characters (usually [Alt+_]-key combinations)?
Press F3. Pls. take then a look at the Format Shape Task Pane, select "sort of" tab Fill & Line and the click on FILL. You see the following items:
No fill
Solid fill
Gradient fill
Pattern fill


Many thanks and greetings
visiofox

[JuneTheSecond]

I am using Visio 2016 pro for Office 365.
In my case, a sequence of Alt, H and U1 adds under line to the text of a selected shape.