Is there a way to import multiple (event) log files with a script?

Yes, EventSentry comes with a log file import utility which can be operated manually (double-click it and navigate the interface) or from the command line. The command-line documentation can be found here.

Here is an example of importing the Security log from all of the evtx files in the "C:\Temp\logs" folder by using a VBS script. Please note that you'll need to move or delete the evtx files when completed to avoid duplicate data resulting from importing the same files multiple times.

Option Explicit

Dim FS, FO, FC, FN
Dim MyFolder, MyExtension, CurrentExtension
Dim MyImporterExe, MyEventlogName, MyActionName, MyCommand, MyShell

MyFolder = "C:\Temp\logs"
MyExtension = "evtx"
MyImporterExe = "C:\Temp\EventSentry\eventsentry_db_import_x64.exe"
MyEventlogName = "Security"
MyActionName = "Primary Database"

Set FS = CreateObject("Scripting.FileSystemObject")
Set FO = FS.GetFolder(MyFolder) 
Set FC = FO.Files

For Each FN in FC
    CurrentExtension = FS.GetExtensionName(FN)
    If MyExtension = CurrentExtension then
        MyCommand = "cmd /K " & Chr(34) & Chr(34) & MyImporterExe & Chr(34) & " /file:" & Chr(34) & MyFolder & "\" & FN.name & Chr(34) & " /eventlog:" & Chr(34) & MyEventlogName & Chr(34) & " /action:" & Chr(34) & MyActionName & Chr(34)
        Set MyShell = WScript.CreateObject("WScript.shell")
        MyShell.run(MyCommand)
    End If
Next