It would probably depended on how long you intend to have the air conditioner.
How to install portable air conditioner in sliding window horizontal.
Installing an air conditioner into a horizontal window which is a window that slides left and right instead of up and down is similar to installing an air conditioner into a vertical sliding window.
It is one of those models that require you to pre plan their permanent position as carrying it around would take three to four persons.
Most inexpensive a c units are designed for vertical sliding windows which creates a problem if you have horizontal sliding windows.
Most of the ones i ve seen are install like this with a timber frame made to sit into the window frame then put the air conditioner inside of the frame and box it out with plywood but this looks like a much neater installation where the frame is made from c channel with a perspex panel above the airconditioner.
Expandable window mounting kit accommodates horizontal sliding or crank out casement windows with a 15 16 min max window width and a 21 39 min max window height 3 speeds in both cool and fan modes.
How i installed my air conditioner.
This is a very simple inexpensive and easy way to install an air conditioner in a slider window without buying an a c made for slider windows.
Installing a c unit inside of a horizontally sliding window.