Switch between adjusting opacity and fill.
Use the preset values you rely on in your workflow.
If you hold down the Alt/Option key, 100% is used.
Switch to the settings, where you can enter your desired values for each button. If you do not enter a value for a button, this button will be hidden.
Reduce/increase the current value by 1%.
If you hold down the Alt/Option key, the current value is reduced/increased by 2%.
If you hold down the Ctrl/Command, the current value is reduced/increased by 5%.
If you hold down the Shift key, the current value is reduced/increased by 10%.
A right-click on a button shows you all available functions, so you don't have to remember the keyboard shortcuts.
There is also an export and import function at the top right of the panel, so you can copy your settings and prompts to another version of Photoshop.