The related list in Lightning Experience can have show only 4 fields as of now whereas you could have 10 in Classic. This may make you little worry while lightning transition from Classic. Nobody want to loose the capabilities he or she has. No worries, there are two ways to solve the problem. Let’s have a look:-

Approach-1

The Summer’19 release comes with an exciting feature to have up to 10 columns in your related list in Lightning. It also allows you to sort, perform mass actions, resize columns and wrap text. Lets see how:-

• Open a record in lightning Experience and click on setup and select edit page option. It will open the page in Lightning App Builder.
• In Lightning App Builder click on your related list Component, it will open properties pane in left hand side.
• In Related List Type option, select the Enhanced list option and magic happens. We were waiting for this functionality for a long time. The related list appears to have more than 4 columns and it can be up to 10.
• You can perform mass action using this related list. If you want to hide the actions, deselect the show list view action bar option.
• You can show up to 30 rows in each related list. Just provide the numbers to number of records to display option in property pane.
• Save the page and activate it.

Approach-2

Lightning App Builder provides you an amazing standard Lightning Component which is called Related List Quick Links. It will show you all the 10 fields which you have in Classic at very first glance.

You need to edit the Lightning page layout using Lightning App Builder.Follow the below steps:-

1. Edit the page to add component on it by clicking the setting icon and selecting the edit page option.
   
2. In the Lightning App Builder, add Related List Quick Links Component on the Canvas by dragging it from left hand side pane.
3. Save your page.
   Hang on, you’re not done yet! To make your customized record page available to your Lightning Experience users, you must activate it. You can activate the page from the Save dialog when you save it for the first time or later using the Activation button.

Approach-3

A Contact record has related list as Opportunity. Whenever user hover over his mouse on the record name in related list, he is able to see different field other than the fields available in related list card. In this way, User will be able to see 9 fields at a time in related list.

Steps to follow:-

1. Go to object manager and select the object referenced in the related list
2. Create a new Compact Layout and select the field which are different from fields already present in related list
3. Assign the compact Layout to the profile

The Compact Layout will consider first five fields whenever you hover your mouse on the name of the record in related list as shown in image.

Consideration:- The Compact Layout will impact the Highlight Panel of the Lightning Page Layout. The same fields will appear there as well.