Is it possible to change and increase the number of days prior to the conversion to more than the default 90 days?

First, go to the Multi Attribution report which is listed under the « Goals » category. In the top you can find a select field where you can change the number of days that should be considered prior to the conversion. By default, you can select 7, 30, 60 and 90 days.

There may be scenarios where you want to increase the number of “Days prior to Conversion” to more than 90 days. By default the maximum number of days is 90 but it is possible to increase the number of days. You have to keep that in mind that it may affect performance of Matomo, the higher the number of days the slower the report processing gets. You can configure which days should be available in your config/config.ini.php file in a comma separated list like this:

[MultiChannelConversionAttribution]
available_days_prior_to_conversion = 7,30,60,90,120
default_day_prior_to_conversion = 30