How to Hide and Unhide folder

How can I hide a folder 
There are multiple ways to hide a folder
1 - Click on the Album Cover. You will see Hide this album button.
2 - You can also click on the Edit button on the top bar of the Album list.
You will see all the folders and will be able to hide some of them. 
This is shown in the screenshots below
 
 
 
How can I unhide a folder 
You just need to do the exact opposite of what was presented above. 

How can I hide completly a folder and all its subfolders?
This is done through the use of the excluded folders feature. 
You will want to do that when you have a Music Player generating tons of photos because of the album covers of the music tracks you have for instance.
This feature is accessible from the Settings page. 
 
 
What about nomedia?
We are not using .nomedia file to hide folders.
The nomedia capability is supposed to be used for apps that want to hide their own filed (like cached photos), not manipulate other apps's folders.
 
 
What is the difference between hiding and securing?
Hiding will just make the folders invisible inside Piktures. It does not hide the files from other apps like File Explorer apps or other Gallery apps.
Securing actually encrypt and move your photos to a secret space inside your phone. It ensures maximum confidentiality of your most private photos.