Linking of folders is a new feature that is available from Avaz version 8.0 onwards.
What is a linked folder?
Linked folder offers views of an existing folder in multiple locations without having to 'copy and paste' the entire folder to various locations, hence making syncing customizations much easier. It maintains one "original" folder and the rest are linked to that original one. This avoids maintaining multiple copies of the same content in different locations.
For example: For a folder like Going to the Doctor (under Topics), you can link the Body Parts folder for ease of access and contextual relevance, though this folder is located elsewhere.
Linked folders have a link (chain) icon in the top left corner for quick identification. Another example of the use of linked folders is COLORS folder which is originally under DESCRIBE folder but can be linked and accessed directly from other folders too, such as CLOTHES, ACCESSORIES, ART AND CRAFT etc.
Advantages of using a linked folder
- Contextual relevance in the vocabulary
Linking folders can help communicators, by making it easier to locate context-specific folders and hence communicate faster. - Reduces navigation effort for the user
- Eases programming effort for the communication partner
It does automatic syncing of customizations across all linked folders. - Maintains motor planning
Linking helps users remember where words are located by keeping the layout the same in different locations.
How to link to an existing folder?
1. Tap Menu.
2. Tap Edit Words.
3. Tap the Add New button or tap the "+" icon if you want to add the folder in a particular location. In this example, we are adding the folder in a particular location by tapping the "+" icon. 
4. Select the Link an existing folder icon. 
5. You are prompted with a search the vocabulary bar on Search folder page.
6. In the Search bar, enter the name of the folder that you want to link, say Colors. The various Folders with this name are displayed. Tick to select the folder that you want to link and tap Done at the top right corner.
7. The selected folder is linked to the particular location in the current page. You will notice a small "chain" icon on the top left corner, to indicate that it is a linked folder. 
Location of the linked folder
When a linked folder is added using Add New > Link to Folder, the linked folder gets added to the same location as in the original folder, provided the target location is empty. This helps the user by keeping the motor planning consistent. If the slot is not empty, it gets added to the end of the same page.
If the linked folder is added using "Add New in Place" (by tapping the Plus icon on the buttons that are empty), it is added in that specific location.
Properties of the linked folder
The linked folder mimics all properties of the original / parent folder (Auto-back, different grid size, alphabetical arrangement).
Related articles:
Avaz FAQ: What happens when you edit or delete a linked folder?