It might not surprise you that Dynamics 365 and previous versions of Microsoft Dynamics CRM are often used to input data on forms. In my opinion the CRM system has to facilitate the data input in a way that it causes the least amount of effort for the end-user and provides the fastest way to input said data.
Being able to change the tab order from top-to-bottom to left-to-right might be of great assist in this process.
The one and only way to provide a supported method to change the tab order is by using sections. Each line has to be put in a different section and then the tabbing order will go from left-to-right.
This, however, might not always fit the needs and can be a pain in the ass on an aesthetical level.
I’m definitely not recommending going unsupported but this does fit the needs here. For Dynamics CRM 2011 you can use the code snippet on http://crm.ipiyush.me/tab-order-on-dynamics-crm-2011-forms/ . This indeed works for CRM 2011 but breaks in Dynamics 365.
I have roamed the internet but did not find a working solution so with some DOM inspection and some trial and error I came up with this working solution. Call the onload and you’re good to go.