how to insert a tick?

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Since I don't know what international keyboard you are using, you can choose menu > Edit > Special Characters ... or just press control+command+spacebar. In the left panel of the character viewer, are categories. If you need another category, pick it from the drop-down gear icon in the upper left corner.

Place your insert cursor where you want the symbol inserted. From the character viewer, double-click the symbol (or its font variation) that you want inserted.

The following categories have check mark (tick) characters:

1. Bullets/Stars
2. Math Symbols
3. Emoji (bottom category)
4. Technical Symbols
5. Unicode
   1. Mathematical Operators
   2. Miscellaneous Symbols (including tick in a box)
   3. Dingbats

Go to the "Edit" menu, find "Special Characters..." at the bottom. Look for a suitable tick (search for "check" in the search field) and double click it.