TinyMCE

Editor body

Header 3

Alt + ↑   Shift + 3

All hotkeys for TinyMCE

Editor body
Bold

Ctrl + B

Editor body
Italic

Ctrl + I

Editor body
Underline

Ctrl + U

Editor body
Select all

Ctrl + A

Editor body
Redo

Ctrl + Y

Editor body
Redo

Ctrl + ↑   Shift + Z

Editor body
Header 1

Alt + ↑   Shift + 1

Editor body
Header 2

Alt + ↑   Shift + 2

Editor body
Header 3

Alt + ↑   Shift + 3

Editor body
Header 4

Alt + ↑   Shift + 4

Editor body
Header 5

Alt + ↑   Shift + 5

Editor body
Header 6

Alt + ↑   Shift + 6

Editor body
Paragraph

Alt + ↑   Shift + 7

Editor body
Div

Alt + ↑   Shift + 8

Editor body
Address

Alt + ↑   Shift + 9

Editor body
Focus to menu bar

Alt + F9

Editor body
Focus to toolbar

Alt + F10

Editor body
Focus to element path

Alt + F11

Editor body
Focus to contextual toolbar

Ctrl + ↑   Shift + E then P

Editor body
Insert link

Ctrl + K

Editor body
Toggle fullscreen

Ctrl + ↑   Shift + F

Editor body
Save

Ctrl + S

Editor body
Find

Ctrl + F

Accessibility
Execute command

⤶ Enter

Accessibility
Execute command

Space

Accessibility
Close sub menu

→

Accessibility
Focus next widget

⭾ Tab

Accessibility
Open widget menu

↓

Accessibility
Open sub menu

←

Accessibility
Focus previous widget

↑   Shift + ⭾ Tab

Accessibility
Focus previous widget

↑

Accessibility
Move focus back to editor body

Esc

Similar combinations for other applications

Adobe Premiere Pro (Windows)
Workspace 3
Project panel

Alt + ↑   Shift + 3

Mp3tag
Filename - Filename (Preview)
Convert

Alt + ↑   Shift + 3

Google Sheets (Android)
Apply bottom border
Format cells

Alt + ↑   Shift + 3

Google Sheets
Apply bottom border
Format cells

Alt + ↑   Shift + 3

Sublime Text
Split view into three columns
Split window

Alt + ↑   Shift + 3

Outlook 2016 and Outlook 2013
In a contact form, under Internet, display the Email 3 information
People

Alt + ↑   Shift + 3

Microsoft OneNote
Expand to Level 3
Use outlines

Alt + ↑   Shift + 3