How to add a third-party booking widget to your header navigation
The best way to insert a third-party (such as Simple Practice) booking widget into your header navigation button on Squarespace is to insert your client portal link.
On Squarespace 7.1
1. Click Edit on a page on your site.
2. Click Edit Site Header.
3. Click Elements.
4. Switch the Button toggle on.
5. Below, edit the button text and click the gear icon next to the link field.
6. Insert your client portal link and switch the Open in New Window toggle on.
6. Hover over Done and click Save.
On Squarespace 7.0
Refer to these instructions in the Squarespace Knowledgebase.
Learn more about adding and editing buttons on Squarespace here: https://support.squarespace.com/hc/en-us/articles/360000293128-Adding-buttons-to-your-site#toc-header-and-banner-buttons