[SalesForce] Case comments and case custom buttons in the Lightning environment

There is a catch in case of cases and work orders objects when it comes to quick actions. In the article under Actions on record pages there is note that says

Actions on cases and work orders appear in a different way than on other records. On case and work order records, the page-level action menu contains custom buttons and supported standard buttons. Quick actions appear on the Feed tab.

For other objects, you can edit page in the Lightning Experience and then select Salesforce1 and Lightning Experience Actions from the selection panel. The panel states

Actions in this section are predefined by Salesforce. You can override the predefined actions to set a customized list of actions on Salesforce1 and Lightning Experience pages that use this layout....

Once you click override the predefined actions link, it will give you available actions for SF1 and lightning to use. And then position your lightning-action in your desired sequence, as shown below.

I worked on the Account object for this example, it should be no exception for other objects, and this is what I got

It should be noted that you can't add more than three (3) viewable lightning-actions on the page, as shown in the picture above in green square You can display upto 10 actions on page layout, but other action will available when you click the drop-down next to the last button on the right. There is an idea on this to let users display more Action Buttons on Lightning Highlights Panel, you can upvote that if it affects you.

Edit

I have just come across this Page Layouts in Lightning Experience trailhead and it says

The highlights panel, which contains key fields for the record, is the only part of a record page that you can’t customize using the page layout editor. The fields in the highlights panel are customized using a compact layout.

I just edited the highlights panel using page layout editor, strange. May be this trailhead content is old, if someone can put some light on this.

You can create a Visualforce page using the standard list controller, and define it as a list button.

Refer this link: Adding Custom List Buttons using Standard List Controllers

These display as expected in Lightning:

You can create new actions for your objects, in the form of buttons and links, by defining them on an object. JavaScript buttons and links aren’t supported in Lightning Experience, but Visualforce (and URL) items are. The process of defining Visualforce buttons and links is identical to that in Salesforce Classic, so we won’t bother to show it here.

Don't forget the Custom Object must be Searchable in order to add your new button to the List View Search Layout.

You can then use Lightning for Visualforce (Lightning Out) to render a lightning component in your VF page if you're doing a primarily lightning component project.

Trailhead Module: Use Visualforce in Lightning Experience