If you don't need the text color or boldness to be unique or different for each message, you could use a popup menu.
In a table somewhere make a column of all the messages you want in your popup menu. Arrange them in the order you want them. Select them all plus one blank cell and change the format to Pop-up menu. Copy the blank cell and paste it in the cells that might need a message. Now you can choose the message from the list that pops up when you select the cell.
Inthe screenshot below I selected cells B2-B5 and formatted them as pop-up menu. I copy/pasted B5 to D2. I then clicked on D2. I can choose any of those messages from the list and it will appear in D2. You can set the format of the cell to be bold or orange or whatever but all messages will get that same format, it will not be individualized for different messages.
If you need to edit a message or add a new one to the list, select them all again, change the format to Text, make your edits and/or additions, then follow the same steps as before to make a new popup and copy/paste it to the places that need the new one. The existing popups from before will not be affected by the changes (unless you copy/paste over them with the new one).