I believe you're asking how to keep the positions of items in your Bookmarks Bar fixed, so that they do not move when you Sort.  BookMacster has two features to support this.

1.  If you want individual items (either bookmarks or folders) to remain at the top, select them and click in the menu Selection ▸ Sort at Top.

2.  For even more manual control, instead of doing that, select the Bookmarks Bar and click in the menu Selection ▸ Will be Sorted so that the checkmark disappears and the "sorted" icon to the left of the word "Bookmarks Bar" changes to "Unsorted".  Then, no items in your Bookmarks Bar will ever move.  You can do this to any folder.

For related options, click the tab Settings ▸ Sorting and look at the box Which folders will be sorted….