https://galex.dev/posts/how-to-provide-view-ids-in-compose/

ModifierLocalAutomationContext.kt

package com.example.myapplication

import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.modifier.modifierLocalConsumer
import androidx.compose.ui.modifier.modifierLocalOf
import androidx.compose.ui.modifier.modifierLocalProvider
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.platform.testTag
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.semantics.testTagsAsResourceId

private val ModifierLocalAutomationContext = modifierLocalOf { "" }

@OptIn(ExperimentalComposeUiApi::class)
@Composable
fun Modifier.automationContext(context: String): Modifier {
    var prev by remember { mutableStateOf<String?>(null) }
    return this then Modifier
        .modifierLocalConsumer { prev = ModifierLocalAutomationContext.current }
        .modifierLocalProvider(ModifierLocalAutomationContext) {
            if (prev.isNullOrEmpty()) context else "${prev}_${context}"
        }
}

@Composable
fun Modifier.automationIndex(index: Int): Modifier = automationContext("index_$index")

@OptIn(ExperimentalComposeUiApi::class)
@Composable
fun Modifier.automationId(id: String): Modifier {
    val packagePrefix = LocalContext.current.packageName
    var prev by remember { mutableStateOf<String?>(null) }
    return this then Modifier
        .modifierLocalConsumer { prev = ModifierLocalAutomationContext.current }
        .semantics { testTagsAsResourceId = true }
        .testTag(if (prev.isNullOrEmpty()) "$packagePrefix:id/$id" else "$packagePrefix:id/${prev}_${id}")
}