Is there a way to call the existing standard action of Lead Convert inside a custom lighting component? I need to show a modal with some validations and if it seems correct by the user, click inside the modal the Convert standard action/button. Thank you!
There is no interface to convert a Lead directly through Lightning Components.
However you can use your Apex controller for that. Here's the example how to convert Lead programmatically (full reference in Apex Developer Guide: Converting Leads):
Lead myLead = new Lead(LastName = 'Fry', Company='Fry And Sons'); insert myLead; Database.LeadConvert lc = new database.LeadConvert(); lc.setLeadId(myLead.id); LeadStatus convertStatus = [SELECT Id, MasterLabel FROM LeadStatus WHERE IsConverted=true LIMIT 1]; lc.setConvertedStatus(convertStatus.MasterLabel); Database.LeadConvertResult lcr = Database.convertLead(lc); System.assert(lcr.isSuccess());