With your cursor on the standard staff (not the tablature), you can change the direction of the stems using the buttons in your keyboard.
To add a legato slur, turn your keyboard to Alterate using the Alt key, then select the range of beats you want to group with a Legato.
Press this button in the keyboard.
And it will create a legato slur above. Please note that the slur is attached to the staff your cursor was located on when you pressed the key.
You can tap on a slur to let the modification handles appear. You can grab these handles and alter the shape of the slur as you want. (You may want to maximum zoom when grabbing the handles as this can be difficult to get on a small device).
To remove a slur, select it with a tap and press the Delete key.
To add a grace note, tap this button on the keyboard.
This will enter in grace note entry mode. You will notice the cursor turned to red.
In grace note mode, the operations will affect the grace note and not the main note it is attached to.
To delete a grace note, simply press Delete when in grace note mode.
You can have multiple independent voices in the same measure. This is simply called multivoice.
Reflow allows you to manage four independent voices.
To change the active voice you're working on, use this button on the palette.
You will see the button turning to the active voice you're on.
All inactive voices will be grayed out, and you can start entering notes on the active voice.