1. first of all, when you enter the flammable solid mark, you can not only enter it directly by superscript, but also by inserting symbols, that is, position the cursor at the position where you enter the trademark symbol, then click the Insert tab and click Symbol in the Symbol ribbon.

2. Secondly, you can see the trademark symbol in the "Custom" symbol area. Click the mouse directly to insert it into the corresponding position.

3. At last, you don't see it in the "Custom" symbol area. At this time, you can click "Other Symbols", and then click the "Special Symbols" tab in the symbol dialog box to see the flammable solid symbol, and double-click the mouse to insert it into the document.