Signals Notebook: When doing copy/paste of a HELM String with valid monomers some of them are pasted as AA#

Details: This is a known issue that can happen when ChemDrawJS fails to interpret the monomer correctly during the paste operation. As a workaround use the 'Text' feature of the ChemDrawJS HELM Editor to add the string.

Steps:
1. Open the HELM Editor
2. Click on the 'Text' tab
3. Paste the string on the text box
4. Click 'Insert'