Select or Double-click the word you want to edit. This highlights all its occurrences via Smart Highlighting.
Go to the menu:
Edit > Multi-Select All
Here, you will see options like Match Whole Word Only and Match Case & Whole Word.
Choose the appropriate option to select all occurrences of the word as actual selections (multi-cursors), not just highlights1.
Now, all occurrences are selected as editable cursors. You can type to replace or edit all of them simultaneously.
Bonus tip: assign a keyboard shortcut to the menu action. This way you can multi-edit all occurrences of selected text with just a press of a shortcut (just like in sublime)